Does Bariatric Surgery Reset The Setpoint?
As readers are well aware, the crux of the obesity problem is that the body tends to defend it’s highest body weight. This is why anytime you try to lose weight, the complex neuroendocrine kick in to try to “sabotage” your efforts and seemingly won’t rest till the weight is regained.
So why does bariatric surgery work? Why do people who undergo bariatric surgery not simply eat back the extra calories required regain all of the weight they lost in the first year after surgery?
One of the notions is that the surgery itself makes it hard to overeat (restriction) or works by interfering with digestion (malabsorption) – but there is now increasing evidence that neither of these mechanisms appear to be the real reason surgery is so successful.
Now, a study by Zheng Hao and colleagues from Baton Rouge, LA, published in OBESITY, provides evidence to support the idea that gastric bypass surgery may produce favourable long-term outcomes by reprogramming the way that they body regulates its weight.
The studies (performed in mice), show that after Roux-en-Y gastric bypass surgery, the animals begin to regulate body weight at a level that is lower than before surgery.
What was most surprising in these experiments, was that mice which were starved down to a rather low weight before surgery, actually regained weight after surgery (albeit to a weight that is still well below where they would have been before the experiment) and that this weight gain was mainly due to an increase in lean-body mass.
This response is very different from animals (or humans) regaining weight after dietary caloric restriction, where most of the weight gain is due to an increase in fat mass.
Thus, it seems that the neuroendocrine alterations that happen with surgery, trigger mechanisms that appear to defend against a higher level of body fat, while remaining sensitive to the defense of lean mass.
How exactly this works remains unclear but the hope is that by better understanding the molecular and physiological mechanisms underlying this reprogramming we may be able to develop medications that will mimic the effects of surgery.